Barca is currently at -63M, Real at -81M.
Barca probably won't sell and possible could sign aditonal players. Its true that Real will probably sell Di Maria or Khedira so they could balance their transfers, but they will do that if the offer is very good or if the player desires. Otherwise no, they don't have to, all the rest have to.
If we look at the 2013/2014 season the transfer sum:
All the rest had positive sum, including Atletico + 43M, Sociedad +12M
out of 400M EUR spent, Real+Barca spent more then half.
This year the ratio could be even worse.
Proud supporter of Deportivo la Coruna and Slovenia national football team